3-Aminomethyl-3,5,5-trimethyl cyclohexylamine (also known as isophorone diamine (IPDA)) is a raw material for preparing 3-isocyanatomethylene-3,5,5-trimethylcyclohexyl isocyanate (also known as isophorone di-isocyanate (IPDI)), polyamide and the like, it can also be used as a curing agent for epoxy resin.
On an industrial scale, IPDA is achieved as follows: reacting 3-cyano-3,5,5-trimethyl cyclohexanone (also known as isophorone nitrile, IPN) with ammonia to form 3-cyano-3,5,5-trimethyl cyclohexylimine (also known as isophorone imine, IPNI), and conducting a reductive amination reaction between IPNI and hydrogen in the presence of ammonia in a catalytic manner. The reaction process thereof is as following:

U.S. Pat. No. 3,352,913 discloses a method for preparing IPDA in which IPN reacts with ammonia and hydrogen under the action of Group VIII metal supported catalysts. In this method, the mole ratio of ammonia to IPN (hereinafter referred to as cyanamide ratio) is from 10 to 30, the reaction temperature is from 70° C. to 130° C., and hydrogen pressure is 150 atm. Because the reaction of IPN with ammonia resulting in IPNI is a reversible reaction and IPN cannot be totally converted into IPNI, a part of the unreacted IPN is also hydrogenated and formed 3-amino-3,5,5-trimethyl-cyclohexanol (IPAA) which is hardly separated from IPDA. The yield of this method is only 80%.
CN101568516A discloses a method for preparing IPDA, after the imidization of IPN, the feed stream containing IPNI is reacted with hydrogen and ammonia in the presence of a hydrogenation catalyst. This method is characterized in that, after a portion of IPNI has been reacted, the reaction mixture is contacted with a basic compound other than ammonia and/or a basic catalyst to increase the alkalinity of the reaction mixture during the reaction. This method controls the occurrence of direct hydrogenation of unreacted IPN by adjusting the IPNI feed stream to be alkalinity during the reaction. However, the further addition of base will exacerbate the detaching of cyano group in IPN, generating CN− and 3,5,5-trimethyl-2-cyclohexenone. CN− may affect the activity of hydrogenation catalyst and shorten its life. The hydrogenation of 3,5,5-trimethyl-2-cyclohexenone will produce a by-product of 3,5,5-trimethyl-cyclohexanol with an undesired yield of IPDA.
At present, there are defects in all industrial methods for preparing IPDA:    1) As the reaction of IPN with excess ammonia generating IPNI is a reversible reaction, IPN cannot be completely converted into IPNI, which results in a portion of IPN entering into the hydrogenation reaction system and being directly hydrogenated into IPAA.
    2) Under the basic conditions, the cyano group of IPN is extremely unstable and very easy to be detached and forms 3,5,5-trimethyl-2-cyclohexenone, while 3,5,5-trimethyl-2-cyclohexanol, which is the product of hydrogenation of 3,5,5-trimethyl-2-cyclohexenone, is an undesired product. Moreover, because the process of decyanation reaction may produce free CN−, this may lead to a decrease in the activity of hydrogenation catalyst.In the conventional preparation methods, the reaction of IPN with excess ammonia generates IPNI and water, while the generated water binds to the remaining ammonia which makes the reaction system show alkalinity, thus the decyanation reaction of IPN is unavoidable.

Although the method disclosed in CN101568516A lowers the yield ratio of IPAA by increasing the alkalinity of IPNI reaction liquid, the addition of extra base exacerbates the decyanation reaction of IPN.